<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            border: solid;
        }
        .main {
            /* width: 600px;
            height: 600px; */
            position: fixed;
            top: 0;
            bottom: 0;
            left: 0;
            right: 0;
            display: flex;
        }
        .main .left, .main .right{
            flex-basis: 100px;
        }
        .main .center {
            flex-grow: 1;
            display: flex;
            flex-direction: column;
        }
        .main .center .top, .main .center .bottom {
            flex-basis: 100px;
        }
        .main .middle {
            flex-grow: 1;
        }
    </style>
</head>
<body>
    <div class="main">
        <div class="left">left</div>
        <div class="center">
            <div class="top">top</div>
            <div class="middle">middle</div>
            <div class="bottom">bottom</div>
        </div>
        <div class="right">right</div>
    </div>
</body>
</html>